Advanced/ZP does the same thing. Not sure if the PB570 is doing it for the same reasons, but in the case of the ZP, I looked into it a while back and it turned out to just be a motherboard DIP switch setting or something like that--the idea being, if you wanted the real machine to work properly, you had to set the DIP switches to tell the mobo what speed CPU you had installed, and it would then be reported in the POST based on the positions of those switches.
Emulating the DIP switches themselves as a configurable user setting would be the most technically correct thing to do here, but perhaps a bit ridiculous and not really necessary. The more reasonable solution would probably just be to add a few lines of code for each mobo that uses this sort of CPU detection, which would simply need to map the appropriate values (derived from the CPU setting in the active PCem config) to the memory or I/O locations where they're expected to appear. Each mobo's documentation generally makes it clear which memory or I/O locations these are and how the board uses them to determine the CPU setting (or at least, the ZP's documentation certainly makes it clear from what I recall).
I actually started the process of implementing this a while back but life got in the way and I doubt I'll be able to get it wrapped up anytime soon, so if anyone else wants to take care of some low-hanging fruit, have at it...
